The invention relates to improvements in security features in paper and other substrates, and in particular to an activatable feature to warn of tampering.
Documents of value and means of identification, such as banknotes, passports, identification cards and the like, are vulnerable to copying or counterfeiting. The increasing popularity of colour photocopiers and other imaging systems, and the improving technical quality of colour photocopiers, has led to an increase in the counterfeiting of such documentation. There is, therefore, a need to improve the security features of such documentation, or paper, to add additional security features or to enhance the perceptions and resistance to simulation of existing features. Steps have already been taken to introduce optically variable features into such documentation which cannot be reproduced by a photocopier. Furthermore, features are now available which are discernible by the naked eye, but invisible to, or viewed differently by, a photocopier. Known examples of such security features include watermarks, embedded and windowed security threads, fluorescent pigments and the like.
However, in addition to attempting to reproduce security features, counterfeiters also endeavour to tamper with or remove information or print or other security indicators associated with documents by immersing the document in water or a solvent.
It is therefore an object of the present invention to provide an improved security feature for a security document which services as an indicator of tampering of the document.
According to the invention there is provided a security feature for a security document comprising at least one activatable layer and at least one visually apparent masking layer, the at least one activatable layer comprising a composition which is generally nonmobile but which becomes mobile when wetted with a liquid, the composition further including at least one detectable component, in which under dry conditions the at least one masking layer wholly covers the activatable layer and renders it nondetectable.
A security feature as claimed in claim 1 in which the composition becomes mobile when wetted with an aqueous liquid.